I. Field of the Invention
This invention relates generally to implantable medical devices in which an electronic circuit and a power source are contained within a hermetically sealed enclosure and having a feedthrough with multiple input and output pins, and more particularly to a connector port for such a device for facilitating the attachment of electrodes on a lead to the input and output pins for the circuitry within the hermetically sealed enclosure.
II. Discussion of the Prior Art
Over the past 30 years great strides have been made in increasing the functional performance of and decreasing the physical size of implantable medical devices, such as those designed for cardiac rhythm management and neural stimulation. Generally speaking, current state-of-the-art implantable medical tissue stimulating devices incorporate a battery power supply and a microprocessor-based controller that is designed to control a pulse generator, causing it to issue pulses at times determined by the microprocessor-based controller. The pulses are conveyed to target tissue on or in the heart by means of one or more medical leads having sensing/stimulating electrodes at a distal end and the electrodes connected by lead conductors to electrical contacts on a connector pin located at the proximal end of the lead. The lead connector connects the lead to the pulse generator.
While a variety of lead connectors have been devised, a major improvement in lead connectors has been the low profile, in-line bipolar design. An in-line connector places both electrical terminals on a single lead pin, with an insulating barrier separating the anode contact from the cathode contact. To facilitate compatibility between pulse generators and leads of differing manufacturers, standards have been developed. More particularly, a joint IEC and International Standards Organization (the International Pace Standards Working Group) has defined the parameters of a low-profile connector referred to as IS-1 for unipolar and bipolar leads and DF-1 for defibrillator leads.
Additionally, there is ongoing work to develop AAMI and Potentially ISO standards for connectors for tripolar and quadrapolar leads.
As those skilled in the art appreciate, the lead connector must be mechanically and electrically secured to the implantable device in a way that remains secure following implantation, but which can be readily detached if and when it becomes necessary to install a new pulse generator. The Persuitti et al. U.S. Pat. No. 6,044,302 describes a connector port for an implantable pulse generator that can accommodate a plurality of in-line lead terminal pin having multiple contacts. In the '302 patent, a lead port has one or more connector blocks each including a set screw to lock the lead connector in contact with the connector block. The connector blocks are, in turn, connected to a feed-through wire. A single elastomeric seal is provided within the port such that when the connector pin is inserted therethrough, it precludes ingress of body fluids into the bore in the header. It is also known in the art to provide sealing rings on the lead terminal connector itself for creating a fluid impervious seal upon insertion of the lead into a connector port. In this regard, reference is made to the Hawkins et al. U.S. Pat. No. 6,029,089.
Prior construction techniques have relied on radial insertion of seal members into a connector bore as well as the use of adhesives to provide bonding and/or sealing. This prior art method exhibits three primary disadvantages. The first is that radial or side loading of the inner seals into the connector block assembly is often a problematic assembly step that can result in non-uniform loading and subsequent deformation of the seal. This creates not only a inferior manufacturing process, but the resultant deformation often translates into highly variable insertion forces between the lead connector and the connector port. Secondly, multi-port device connectors using radially loaded seals often integrate seals between lead bores to help reduce the manufacturing impact. This creates the potential for cross-chamber leakage, since the lead barrels are no longer isolated by the material comprising the connector block. Finally, conventional radial or side-loaded seals often rely on the application of additional medical adhesive to bond and retain the seals inside the header. This results in an undesirable manufacturing process in that the adhesive requires additional steps and frequently ends up in unintended areas.
A need, therefore, still exists for a connector port for an implantable medical device capable of accommodating multiple feedthrough pins and lead connector contacts that remain small in size, easy to assemble, and which exhibits a low insertion force. The present invention provides an efficient and effective means for manufacturing sealed, axially aligned, multi-electrode connector ports for use with implantable medical devices that minimizes the need for medical adhesives. The connector port of the present invention provides mechanical retention, sealing and electrical contact with mating, slidable, smooth, implantable lead connectors.